I'm not sure if this is the right place to post this but............I have a pile of power tool batteries that are bad and am trying to save a few bucks and rebuild them myself. I bought some 2.8 mah sub c nicad batteries to rebuild a pack that was originally rated at 2.4(which I assume is fine to do). I organized the batteries like the old ones and soldered them in place. When I put them on charge, they charged for about five minutes and the charger cut off saying fully charged. I attached it to my drill and it had very little power. It turned the drill but I could stop it by hand, which I shouldn't be able to do. I then tried a different charger and the same thing happened. So now I am puzzled. Are the batteries bad? Well.....it is an 18 volt pack so I used 15 1.2 volt batteries and they are checking at 21 volts. I'm not sure why its too high but I assume that's okay. Could the chargers be bad? Could the thermistor n the pack be bad? I'm at a loss as to what to do next..........Any advice would be greatly appreciated!

I've ran into that problem a few times when rebuilding stock Craftsman battery packs with a higher capacity and quality type of cell.

The thing I do once the battery pack is assembled and working is to put a moderately sized low resistance load on it and let it suck the battery flat dead overnight then put it on the charger for a full 24 hours. A lot of times they will go green within a few minutes then switch back to red charge mode over the next few hours and charge up all the way.